Adjustable trip



W. H. EDMUNDS ADJUSTABLE TRIP NCDV. 6, 31951 2 SHEETSSHEET 1 Filed April8, 1949 ZNVEN TOR. V104 A //W Harm .0 fww/vovg Nov 11951 H EDMUNDS2,574fl93 ADJUSTABLE TRIP Filed April 8, 1949 2 SHEETSSHEET 2 @W N MAttmzey Patented Nov. 6, 1951 ADJUSTABLE TRIP William Harold Edmunds,Havertcwn, Pa as= signer to l-T-E Circuit Breaker Ccmpany, Philadelphia,Pa, a corporation of! Pennsylvania Application April 8, 1949, Serial No.36,135

(Cl. 2ll88) 4 Claims. Z1

My present invention relates to adjustable instantaneous and time delaytripping mechanisms for circuit breakers, and more particularly to anarrangement of a combined thermal magnetic tripping device for a circuitbreaker so that the air gap of the instantaneous magnetic trippingportion of the device and the trip point of the thermal element of thedevice may be readily adjusted from outside the breaker casing withoutthe necessity for opening the breaker casing and without the need forspecial tools of any kind.

It is, of course, well known that a variation in the air gap between thearmature and magnet of a tripping device will result in the variation ofthe tripping point of the circuit breaker.

Likewise, an adjustment of the position of the thermal member or anadjustment of the mechanical force, such as a spring which the thermalmember must overcome in order to trip, will result in variation of thetime delay tripping of a thermal magnetic breaker.

Heretofore, however, such adjustments, especially in the small circuitbreaker field, were factory made and were not subject to variation inthe field, except by opening the casing or housing of the circuitbreaker and changing the relative position of the elements therein.

My invention is directed to a simplified means for adjusting the air gapbetween the armature and the magnet and for adjusting the trippingposition of the thermal element of the tripping device from outside thecase without the necessity for opening the casing or housing of thecircuit breaker and tampering with the interior thereof.

Essentially, my invention contemplates the mounting of the armature ofthe magnet in such a manner that by rotation of a simple memberextending outside the casing, the armature may be moved closer to themagnet to decrease the air gap or further from the magnet to increasethe air gap.

In order to accomplish this result, a simple rotatable cam accessiblefor operation from the outside of the circuit breaker bears against anelement connected to the armature. The rotation of the cam moves theelement which is connected to the armature and hence the armature itselfcloser to the magnet; rotation of the cam in an opposite directionpermits the armature biasing means which normally maintains the armatureaway from the magnet to withdraw the armature from the magnet.

Also, my novel device contemplates a rotatable element accessible fromoutside the circuit break= er and operable either to increase thecompression of a spring against which the thermal element must operatein order to trip the circuit breaker or to increase the degree ofengagement of the thermal element with the latch within the circuitbreaker.

The primary object of my invention, therefore, is the provision of novelmeans accessible from outside the circuit breaker for adjusting the airgap between the magnet and armature of an instantaneous tripping device.

Another object of my invention is the provision of novel meansaccessible from outside the casing of the circuit breaker for adjustingthe tripping point of a thermal unit of a time delay tripping device ina circuit breaker.

Another object of my invention is, in a combined thermal magnetictripping device, apparatus operable from outside the casing of thecircuit breaker for adjusting the air gap of the magnetic element of thetripping device.

Another object of my invention is, in a thermal magnetic trippingdevice, the provision of novel means operable from outside the breakercasing for adjusting the tripping point of the thermal device.

Another object of my invention is, in a combined thermal magnetictripping device, means operable from outside the circuit breaker casingfor adjusting the air gap of the magnetic element of the tripping deviceand the tripping point of the thermal element of the tripping device.

The foregoing and many other objects of my invention will becomeapparent from the following description and drawings in which Figure 1is a side elevation partly broken away of a circuit breaker embodying mynovel adjustable thermal magnetic tripping device.

Figure 2 is a view partly in cross-section taken on line 2-2 of Figure1, looking in the direction of the arrows, showing the magnetic elementof my novel tripping device.

Figure 3 is a view in persepctive showing the carrying element for theadjustment to my magnetic tripping element.

Figure 4 is an enlarged detail view showing the operation of theadjustable element of the magnetic section of my novel tripping device.

Figure 5 is a fragmentary detail view of one of the embodiments of thethermal tripping device and the adjustment thereof.

Figure 5A is a sectional detail of the thermal 3 adjusting screw takenalong line 5A--5A of Figure 5.

Referring now to the figures, the circuit breaker i is enclosed in thecasing II and is provided with a lower connecting terminal 12 connectedby the pigtail l3 to the thermal trip unit M.

The thermal trip unit 14 is in turn connected to the energizing coil iof the tripping magnet l6. Current then passes through the coil 15 tothe terminal l1 and through pigtail E8 to movable contact arm 19 and themovable contact l9a. Current then passes to the stationary contact 20when the circuit breaker is closed and through the short bus 2i to theupper connectin terminal 22.

The circuit breaker contacts are maintained latched in closed positionby the latching element 23 engaging under the latching detent 24, whichlatching detent 24 is rotatably mounted on the cross-shaft 25.

A crank 26 on the cross-shaft is bifurcated to pass on either side ofthe rod 21 which passes through the thermal trip sleeve 29 and supportsthe instantaneous tripping armature 28. When armature 28 is attracted tothe magnet 16, the armature supporting rod adjustment nut 3! strikes theright-hand end 29a of the thermal tripping sleeve 29 with respect toFigure 1, and the tripping flange 30 on the thermal trip sleeve 29strikes the crank 26 and rotates shaft 25 and latching detent 24clockwise with respect to Figure 1 to disengage latch 23 and permit thecircuit breaker 10 to trip.

The circuit breaker I8 may be of any well known standard type similar tothat shown in Patent No. 2,421,853.

The invention here relates to the adjusting elements 32 for adjustingthe air gap between the armature 28 and magnet l6 and the adjustingelements 33 for adjusting the tripping point of the thermal unit,without removing the cover of the circuit breaker enclosure.

The tripping magnet I5 is mounted in a recess 34 (Figm'e 1) of thecasing I], and the armature 28 is slidable in the said recess. Thearmature 28 is preferably rectangular and is guided by the sides of therecess so that it cannot rotate with respect thereto.

The armature support rod 21 extends through the thermal trip sleeve 29to the right-hand end 2911. The support member 36 (Figure 3) comprisesthe parallel legs 31, 31 and the base flanges 38, 38 which are securedin any suitable manner, as by the bolts 39, to an appropriate portion ofthe interior of the casing. Stationary cross member 48 is carriedbetween the legs 31, 31 of the supporting member 36 and is provided withan opening 4| through which the thermal trip sleeve 29 passes.

The armature support rod 21 terminates at its right-hand end 21a,against the stud 53 of the armature air gap adjusting knob 5|].

Tension springs 45, Figure 2, are connected between stationary lugs 46,46 extending from the outer section of the support 36 and lugs 41, 41 onthe armature 28. The tension springs 45 thus serve to hold the armature28 away from themagnet 16, the maximum distance being determined by thepoint at which the outer ends of the lugs 41 bear against the under-sideof the flanges 38. This is the maximum air gap which can be provided.

The air gap adjusting knob 50, the top of which is accessible throughthe opening 5! in casing II and which is provided with a slot 52 or anyother appropriate recess so that the same may readily be rotated fromthe outside of the casing, has an inwardly extending stud 53, theleft-hand end of which bears against the rightnanu end 21a of thearmature support rod 21. A pin 55 carried by the stud 53 of knob 55extends into the oetents 63 of the cam surface 51 of the tubular camsection 55.

The compression spring 68 hearing between the outer surface 35 of thesupport 36 and the under-side of the knob 50 pulls up the stud 53 andthe pin 55 into the detents 63 of the cam section 54. The tensionsprings 45, above described, pull the armature 28 and hence the armaturesup port rod 21 against the stud 53 and therefore the pin 55 against thedetent 63 in the cam section 53. This serves to maintain the particularsetting which must be reached.

In order to operate the element to a new setting, it is necessary topush the knob 50 in with a screw driver in recess 52 to clear the pin 55from detents 63 in the tubular cam section 54 and then to rotate thestud 53 which will cause the pin 55' to ride out of one detent 63 to thenext detent 63. Due to the spiral nature of the cam surface 51 of thetubular cam section 53, each succeeding detent 63 will cause the stud 53to be nearer or farther away from the magnet 16 in accordance with thedirection of rotation of the knob 50. Thus by bearing against theleft-hand end 21a of the armature support rod 21, the stud 53 can varythe air gap between the armature 28 and the trip magnet I6.

By this means, therefore, a simple rotation of the knob 50 will resultin pushing the rod 21 into the circuit breaker housing when rotation isin one direction and will result in the tension springs 35 pulling therod 21 out toward the outside of the circuit breaker housing when therotation is in the opposite direction. This will correspondinglydecrease or increase the air gap between armature 28 and magnet l6.

An indicating arrow 18 may be placed on the outer surface of the knob 50to cooperate with an appropriate scale indicating the condition of theair gap preferably in terms of tripping current values or in the numberof times the normal current of the circuit breaker at which it will tripfor the particular angular position of the knob 50 and hence for theparticular air gap between the armature 28-and the magnet I6;

In appropriate cases, the cam surface 51 may be sloped so that equalincrements of rotation of the knob 50 will result in equal increments inthe required current flow in the trip magnet for operating the armature.Since magnetic flux across the air gap between the magnet I6 andarmature 28 varies inversely as the square of the distance, it will beobvious that progressively smaller movements of the armature toward themagnet will be necessary for equal increments in the flux as thearmature approaches the magnet decreasing the air gap.

It will also be obvious that progressively increased movements of thearmature 28 from the magnet I6 will be necessary for equal decreases inthe magnetic flux asthe armature is adjusted away from the magnet.

The slope of cam 51 may thus be arranged so that equal increments ofrotation of knob 50 will result in equal increments in the currentresponse of the magnet. For this purpose, the slope should be relativelyfiat at the position where the armature is furthest from the magnet andrelatively steep at the position where the armature is closest to themagnet, varying progressively on a logarithmic curve between these twopositions.

While I have shown the knob 58 as flush with the casing II so that itmay be made accessible simply by using a screw driver in the slot 52, itwill be obvious that the knob 58 may be extended out of the casing II tobe manually grasped or operated on by a tool embracing the knob; and theknob 58 may be extended sufliciently so that it is accessible fromoutside a switchboard panel without the necessity for opening the panelto uncover the outer surface of the circuit breaker casing. In theoperation of thermal magnetic circuit breakers, it is also necessary, inorder to produce a time delay trip, at values below that at which aninstantaneous trip is obtained, to provide a thermal unit II.

The thermal unit I8 is provided with a latch 88 at its outer endengaging the latch lever 8| which is. pivoted on a cross shaft 82mounted between the legs 3101 the trip unit support 88. Latch lever 8|extends out to where it bears at 88 against the adjustable nut 84 on thethermal trip sleeve 28." A compression spring 88 between the platform 48and the latch lever 8| biases the lever 8| in a counterclockwisedirection with respect to Figure 1 so that section 83 of lever 8| willpush the thermal trip sleeve 28 to the left with respect to Figure 1 tocause a tripping operation to occur when the latch 88 at the end of thethermal unit 48 releases the end of lever 8| to permit rotation thereof.

In order to provide an adjustment for the thermal unit element 14 andthe latch 88, I mount a compression spring 98 on the threaded stud 9|,which stud is received in the tapped opening 92 in wall Ila of casingII.

A lever 94 on the end of the stud 8| will rotate the stud and hencecause it to move back and forth longitudinally in the tapped opening'92, thus causing the compression spring 98 to move inwardly toward theend of the thermal trip unit I4 or away therefrom.

Rotation of lever 98 which is, of course, accessible from outside thecasing II thus increases or decreases the distance of the end ofcompression spring 88 from the end of the thermal element I4. This thenpermits the thermal element II to deflect a greater or smaller distancebefore it reaches the spring 88.

Spring 98 will then retard the deflection of the thermal element. Sincethe torque decreases as the deflection increases, the location of thespring controls the adjustment; the circuit breaker will not trip untilthe thermal element has deflected sufliciently for the latch 88 thereofto disengage the lever 8|.

In Figure 5 I have shown a modified form of adjustment for the thermalelement I4 and its latch 88. This adjustment operates by increasing ordecreasing the engagement of latch 88 with lever 8|.

The pin I88 engages with the latching stud 88. Pin I88 has a spiralthread which meshes with the thread of the tapped opening I 8| in thecasing. I

Lever [82 which is accessible from the outside of the casing adjusts thelongitudinal position of the pin I 88. The rotation of lever I82 thusmoves the pin I88 in and out to adjustthe longitudinal position of thelatch 88 with respect to the end of the lever 8| and thus to adjust thedegree of engagement therebetween. This varies the amount of deflectionnecessary to obtain a trip.

Lever I82 and the lever 94 may operate over a calibrated scale in orderto translate the adjustment into current values to which the thermalunit is responsive for tripping the circuit breaker.

I claim:

1. In a circuit breaker for protecting a circuit, said circuit breakerhaving a pair of cooperable contacts,-having a contact engaging positionand a contact disengaging position; biasing means for biasing saidcontacts to their disengaging position; a latching mechanism formaintaining said contacts in their engaging position against the actionof said biasing means; a trip mechanism for operating said latchingmechanism to release said contacts for operation by said biasing meansto their disengaged position; an electromagnet having a pole face and anarmature spaced from said pole face and operable in response to faultcurrent conditions in the circuit protected by said circuit breaker foroperating said trip mechanism; an armature support rod connected to saidarmature; a sleeve on said rod operable for engaging and operating saidtrip mechanism, a lever arm for engaging said sleeve, means for biasingsaid lever arm against said sleeve; a latch device for engaging andmaintainin said lever arm out of operating relation with said sleeve; athermal unit comprising a bimetal operable in response to fault currentconditions in said circuit for operating said latch device out ofengagement with said lever arm to permit said last-mentioned biasingmeans to operate said lever arm against said sleeve; an insulationhousing for said circuit breaker hav: in a front wall, an operatinghandle for operating said movable contacts into engagement. said handleprotruding through the front of said housing, an adjusting screwengaging said support rod for adjusting the spacing of said armaturewith respect to said pole face, an opening in the front wall of saidinsulation housing adjacent said adjusting screw for providing accessibility to said adjusting screw from outside and in front of saidhousing, a spring positioned in the path of movement of said bimetal,and a second adjusting screw accessible outside of and from the front ofsaid housing for adjusting said spring to vary its action on saidbimetal.

2. In a circuit breaker for protecting a circuit, said circuit breakerhaving a pair of cooperable contacts having a contact engaging positionand a contact disengaging position; biasing means for biasing saidcontacts to their disengaging position; a latching mechanism formaintaining said contacts in their engaging position against the actionof said biasing means; a trip mechanism for operating said latchingmechanism to release said contacts for operation by said biasing meansto their disengaged position; an electromagnet having a pole face and anarmature spaced from said pole face and operable in response to faultcurrent conditions in the circuit protected by said circuit breaker foroperating said trip mechanism; means for releasing said trip mechanism;a latch device for engaging said means; a thermal unit comprising abimetal operable in response to fault current conditions in said circuitfor operating said latch device out of engagement with said means; aninsulation housing for said circuit breaker having a front wall; anoperating handle for operating said movable contacts into engagement,said handle protruding through the front of said housing; an adjustingmechanism for adjusting the spacing of said armature with respect tosaid pole face; an opening in the front wall of said insulation housingadjacent said ad justing mechanism for providing accessibility to saidadjusting mechanism from outside and in front of said housing; a springpositioned in the path of movement of said bimetal and a secondadjusting mechanism accessible outside of and from the front of saidhousing for adjusting said spring to vary its action on said bimetal.

3. In a circuit breaker for protecting a circuit, said circuit breakerhaving a pair of cooperable contacts having a contact engaging positionand a contact disengaging position; biasing means for biasing saidcontacts to their disengaging position; a latching mechanism formaintaining said contacts in their engaging position against the actionof said biasing means; a trip mechanism for operating said latchingmechanism to release said contacts for operation by said biasing meansto their disengaged position; an electromagnet having a pole face and anarmature spaced from said pole face and operable in response to faultcurrent conditions in the circuit protected by said circuit breaker foroperating said trip mechanism; an armature support rod connected to saidarmature; a sleeve on said rod operable for engaging and operating saidtrip mechanism, a lever arm for engaging said sleeve, means for biasingsaid lever arm against said sleeve; a latch device for engaging andmaintaining said lever arm out of operating relation with said sleeve;an adjustment screw for adjusting the spacing of said armature withrespect to said pole face; a. cam surface having detents, a pin seatablein any one of said detents and operable by said screw from detent todetent, said rod being engaged and operable by said screw as said pin isseatable in different detents for changing the air gap of said armatureto said pole face; an insulated housing for said circuit breaker havinga front wall; an operating handle for operating said movable contactsinto engagement; said handle protruding through the front wall of saidhousing; and

an opening in the front wall of said housing adjacent to said adjustmentscrew.

4. In a circuit breaker for protecting a circuit, said circuit breakerhaving a pair of cooper-able contacts having contact engaging positionand contact disengaging position; biasing means for biasing saidcontacts to their disengaging position; a latching mechanism formaintaining said contacts in their engaging position against the actionof said biasing means; a trip mechanism for operating said latchingmechanism to release said contacts for operation by said biasing meansto their disengaged position; a sleeve for operating said tripmechanism; a lever arm for oper ating said sleeve; biasing means foroperating said lever arm; a latch device for restraining said lever armagainst the action of said last-mentioned biasing means; a thermal unitcomprising a bimetal operable in response to fault current conditions insaid circuit for operating said latch device out of engagement with saidlever arm to permit said last-mentioned biasing means to operate saidlever arm against said sleeve; an insulation housing for said circuitbreaker having a, front wall, an operating handle for operating saidmovable contacts into engagement, said handle protruding through thefront of said housing; a movable spring positioned in the path ofmovement of said bimetal; a mechanism for adjusting said movable spring;an opening in thefront of said insulation housing; and a means foroperating said mechanism through said opening.

W. HAROLD EDMUNDS.

REFERENCES @ITED The following references are of record in th file ofthis patent:

UNITED STATES PATENTS Number Name Date 241,213 Herrmann May 10, 18811,646,189 Curtis Oct. 18, 1927 2,265,030 Dorfman Dec. 2, 941 2,459,629Dorfman et al Jan. 18, 19%

